Musculoskeletal injuries and degenerative bone and joint diseases can be disabling. Those affected can suffer from reduced mobility and range of motion in addition to experiencing discomfort and pain. The joint of an animal refers generally to the location within the body where two bones are attached in close proximity. Joints are arranged to allow movement and provide structural support. In general, the two bones at the joint are separated by layers of articular cartilage on the opposing surfaces of the two joining bones with a synovial cavity containing synovial fluid between the layers of articular cartilage to provide lubrication for movement at the joint. The synovial cavity is further enclosed by a synovial lining surrounding the joint. Additional connective tissues including ligaments hold the bones at the joint together by attachment to the opposing bones. Similarly, tendons further connect muscle to one of the bones to allow for mechanical movement. Many injuries, conditions and diseases involve the joint and surrounding tissue.
Following injury or tissue damage, tissues may regenerate new functional cells either by division of existing functional cells or by differentiation of stem cells present in the tissue to form new functional cells. However, unwanted scar tissue may also form as part of the normal healing process which might impair regeneration and elasticity. Recently, stem cell transplants have been proposed as a treatment option for degeneration, damage or injury of the joint and other musculoskeletal tissues to promote tissue regeneration and restore function and performance while reducing pain and discomfort to the animal. These approaches are aimed at tipping the balance away from non-functional repair mechanisms and toward regeneration of functional cells. But, what are needed in the art are improved methods and compositions for isolating and activating particular stem cell fractions for the treatment of these diseases and conditions.